1 files changed, 41 insertions, 0 deletions
diff --git a/node_modules/csso/lib/restructure/prepare/index.js b/node_modules/csso/lib/restructure/prepare/index.js
new file mode 100644
index 00000000..fc08082e
--- /dev/null
+++ b/node_modules/csso/lib/restructure/prepare/index.js
@@ -0,0 +1,41 @@
+import { walk, generate, keyword as resolveKeyword } from 'css-tree';
+import createDeclarationIndexer from './createDeclarationIndexer.js';
+import processSelector from './processSelector.js';
+
+export default function prepare(ast, options) {
+    const markDeclaration = createDeclarationIndexer();
+
+    walk(ast, {
+        visit: 'Rule',
+        enter(node) {
+            node.block.children.forEach(markDeclaration);
+            processSelector(node, options.usage);
+        }
+    });
+
+    walk(ast, {
+        visit: 'Atrule',
+        enter(node) {
+            if (node.prelude) {
+                node.prelude.id = null; // pre-init property to avoid multiple hidden class for generate
+                node.prelude.id = generate(node.prelude);
+            }
+
+            // compare keyframe selectors by its values
+            // NOTE: still no clarification about problems with keyframes selector grouping (issue #197)
+            if (resolveKeyword(node.name).basename === 'keyframes') {
+                node.block.avoidRulesMerge = true;  /* probably we don't need to prevent those merges for @keyframes
+                                                       TODO: need to be checked */
+                node.block.children.forEach(function(rule) {
+                    rule.prelude.children.forEach(function(simpleselector) {
+                        simpleselector.compareMarker = simpleselector.id;
+                    });
+                });
+            }
+        }
+    });
+
+    return {
+        declaration: markDeclaration
+    };
+};